1. Field of the Invention
This invention relates to a radiation image recording and reproducing system for exposing a stimulable phosphor sheet to a radiation carrying image information to have the image information stored thereon, exposing the stimulable phosphor sheet to stimulating rays which cause the stimulable phosphor sheet to emit light in proportion to the stored radiation energy, reading out the image information by photoelectrically detecting the emitted light, and reproducing the read-out image information as a visible image on a recording sheet.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then exposed to a stimulating ray beam such as a laser beam which causes the stimulable phosphor sheet to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to an electric image signal, and the radiation image of the object is reproduced as a visible image by use of the image signal on a recording medium such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
The radiation image recording and reproducing system using a stimulable phosphor sheet is advantageous over conventional radiography using a silver halide photographic material in that the image can be recorded over a very wide range of radiation exposure and further in that the electric signal used for reproducing the visible image can be freely processed to improve the image quality for viewing, particularly for diagnostic purposes. More specifically, since the amount of light emitted upon stimulation after the radiation energy is stored on the stimulable phosphor sheet varies over a wide range in proportion to the amount of said stored energy, it is possible to obtain an image having desirable density regardless of the amount of exposure of the stimulable phosphor sheet to the radiation, by reading out the emitted light with an appropriate read-out gain and converting it into an electric signal to reproduce a visible image on a recording medium or a display device. The electric signal may further be processed as desired to obtain a radiation image suitable for viewing, particularly for diagnostic purposes. This is very advantageous in practical use.
In the aforesaid radiation image recording and reproducing system, the stimulable phosphor sheet is subjected to recording of image information in an image recording apparatus, and is then sent to a read-out apparatus in which the stimulable phosphor sheet carrying the image information stored thereon is scanned with stimulating rays for carrying out read-out of the image information. Then, a recording sheet is scanned with recording light modulated on the basis of the thus read-out image information, thereby to reproduce the image information on the recording sheet. The reproduced image information is then developed and used for making a diagnosis. The reproduction and the development of the image information on the recording sheet are carried out respectively at an image reproducing section and a development section. The image reproducing section and the development section are often built integrally with each other in a single image reproducing apparatus. Also, the image reproducing apparatus is often connected to a plurality of the image read-out apparatuses and used for reproducing the image information read out in these read-out apparatuses.
In the case where a single image reproducing apparatus is connected to a plurality of the read-out apparatuses as mentioned above, the number of the recording sheets conveyed out of the image reproducing apparatus after reproduction and development of the image information are finished becomes very large. Also, the reproduction and the development of the image information are carried out each time read-out of the image information is finished at each read-out apparatus, and therefore the condition of a plurality of the recording sheets taken out of the image reproducing apparatus after the reproduction and the development of the image information are finished becomes such that the recording sheets with various kinds of image information reproduced thereon are mixed with each other. Therefore, when a plurality of the recording sheets obtained in the manner as mentioned above are used for making a diagnosis, troublesome operations of classifying the recording sheets in accordance with the kind of the image information or the like must be carried out in advance.